This move is seen in positions similar to this one and originating from the Bogo-Indian Defense. The central advance throws cold water on any claims Black has on the kingside. Capturing leads to catastrophe (as will happen in the game), but closing the center with e6-e5 leaves Black with no prospects and a terrible bishop on b7.
8... b4c3 This move is necessary after White has castled, since the knight isn't pinned anymore and is ready to move, leaving the b4-bishop in danger. 9. c2c3  9... f6e4 Carlsen needed a win and embarks on a dangerous enterprise. 10. c3c2  10... f7f5 A natural continuation of the previous move, although it's better to castle.